Reading data from NAND FLASH without ECC is not recommended

Reading data from NAND FLASH without ECC is not recommended

[Polyakov Artem]

Hi all! Sorry for my poor english.
I want to ask - why by default reading from NAND flash provided without
ECC?
I work with Samsung K9F5608U0С 32M flash.
And one interest thing for me is that debug messages show that oob bytes
for ECC are used by system. I mean, after eraseing - all bytes are 0xFF.
But my debug messages shows this:
> write oob(00001890): 65 55 97 5a ffff 69 57 ff ff ff ff ff ff ff ff
bytes for ECC are not equal 0xFF!
but system dont use this bytes for ECC correction:
> Reading data from NAND FLASH without ECC is not recommended

Re: Reading data from NAND FLASH without ECC is not recommended

[David Woodhouse]

On Mon, 2006-05-15 at 03:54 +0000, Polyakov Artem wrote:
> But my debug messages shows this:
> > write oob(00001890): 65 55 97 5a ffff 69 57 ff ff ff ff ff ff ff ff
> bytes for ECC are not equal 0xFF!
> but system dont use this bytes for ECC correction:
> > Reading data from NAND FLASH without ECC is not recommended 

You're saying that the system _writes_ ECC data to the flash, but does
not use ECC when reading from the flash?

Please show your NAND board driver, and also the code you used for
reading from the flash.

-- 
dwmw2

Re[2]: Reading data from NAND FLASH without ECC is not recommended

[art]

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Hello David,

Wednesday, May 17, 2006, 6:36:46 AM, you wrote:

DW> On Mon, 2006-05-15 at 03:54 +0000, Polyakov Artem wrote:
>> But my debug messages shows this:
>> > write oob(00001890): 65 55 97 5a ffff 69 57 ff ff ff ff ff ff ff ff
>> bytes for ECC are not equal 0xFF!
>> but system dont use this bytes for ECC correction:
>> > Reading data from NAND FLASH without ECC is not recommended 

DW> You're saying that the system _writes_ ECC data to the flash, but does
DW> not use ECC when reading from the flash?

DW> Please show your NAND board driver, and also the code you used for
DW> reading from the flash.

Setup mtd device from NAND board driver:

        /* Set address of NAND IO lines */
        this->IO_ADDR_R = (void __iomem *)adm5120_fio_base;
        this->IO_ADDR_W = (void __iomem *)adm5120_fio_base;
        /* Set address of hardware control function */       
        this->hwcontrol = adm5120_hwcontrol;
        this->dev_ready = adm5120_device_ready;
       /* 20 us command delay time */
       this->chip_delay = 20;
       this->eccmode = NAND_ECC_SOFT;

and I attach nand_base driver from my kernel.


-- 
Best regards,
 art                            mailto:art@sigrand.ru

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Re: Re[2]: Reading data from NAND FLASH without ECC is not recommended

[David Woodhouse]

On Wed, 2006-05-17 at 14:28 +0700, art wrote:
> and I attach nand_base driver from my kernel.

Either this is the same as the one in the current kernel tree, or it's
the one from 2.6.16, or I don't care at all. Which of the three?

-- 
dwmw2